Problems with 07 YBR 125 revving/starting. Fuel pump/spark!?

[AlsGriffs]

Hi there!
Newish to the forums, although not new to fixing problems to do with bikes. This however is my first FI motorcycle and don't want to start disconnecting things without some guidance first.

A little backstory. The Sunday just gone I was riding home from a friends house, and every now and again the bike would bog out, lurching me forwards (the same way a bike does when you've ran the tank dry! We've all done it!).

The problem got worse and worse as the journey progressed. I may be wrong, although it seemed to effect the higher gears more, as down shifting seemed to fix, maybe due to the revs being low and not needing as much fuel to pull in the higher gears, a blockage of some sort may have injected even LESS fuel.

The problem then started effecting lower gears, until it was doing it in first. Eventually the bike cut out.

I coasted to the side of the road, tried to start it, and after a while it finally fired back up.

Now, the needle was flicking up to 1000rpm, then back to 0, the rev sound matching the fluctuation (vrum 'pause' vrum 'pause' vrum ect.).

Eventually it get a small period where it would finally rev up back to normal, but wouldn't last long until it started playing up again, regardless I managed to limp it home.

Now it's sat on the driveway, the problem still happens. I can video what's happening if it helps. I suspect something to do with the fuel pump/lines. Other thoughts are the spark plug and someone even mentioned oil, it is due for a change.

I was just wondering anybody else's take on this? Have any of you experienced similar problems?

Thanks,
Griff.
____________________
50 grand and 50 miles doesn't make you a biker.

[simonjb]

I've got an 08 YBR and can't say I've had this particular issue, but if you have yourself a Hayne's manual for it (highly recommend) it'll be a lot easier. It's difficult to tell what's going on, but follow the procedure for checking the spark plug (ensure it's clean and spark gap is correct), and check the injector, should be fairly consistent (think the hayne's manual covers it). A way to rule out a faulty fuel pump, when you switch the ignition on, listen to it prime (should pump for a few seconds - put your ear by the tank), see if it sounds consistent. If there's an issue with the fuel injection, check that no lines are blocked, as the injector itself might be ok!

Hope this helps, good luck!

[Eddie Hitler]

When I had those symptoms with my old FMX, it turned out to be the coils failing. Best start would be to test the spark plug.

[AlsGriffs]